Turbo-machines such as compressors and turbines generally include a rotating assembly having a centrally located rotor shaft and a plurality of rows of rotating blades attached thereto, and a corresponding plurality of rows of stationary vanes connected to the casing of the turbo-machine and interposed between the rows of rotating blades. A working fluid such as air or combustion gas flows through the rows of rotating blades and stationary vanes to transfer energy between the working fluid and the turbo-machine.
A rotating blade of a turbo-machine typically includes a root section attached to the rotor, a platform section connected to the root section, and an airfoil section connected to the platform section on a side opposite from the root section. The lateral side edges of platform sections of adjacent blades in a row of blades abut each other to form a portion of the boundary defining the flow path for the working fluid. While it would be desirable to have adjacent platforms abut in a perfect sealing relationship, the necessity to accommodate thermal growth and machining tolerances results in a small gap being maintained between adjacent platforms. Similarly, arrangements of the stationary vanes that are connected to the casings are in need of a seal between respective adjacent vane members.
Prior art turbo-machines have incorporated many types of devices to seal the gap between the platforms of adjacent blades, and also to provide a mechanical damping there between. For low temperature applications such as a compressor, U.S. Pat. No. 4,422,827 provides a seal of a thin strip of silicone rubber, while U.S. Pat. No. 4,580,946 teaches the use of an elastomeric material or a particular shape to seal the gap between adjacent blade platforms. For higher temperature applications such as a combustion turbine, U.S. Pat. Nos. 4,326,835 and 5,281,097 teach the use of a metal plate affixed under the platforms of adjacent blades to seal the gap.
Seals that comprise a ceramic component also are known in the prior art for turbo-machines. For example, U.S. Pat. No. 6,832,892 teaches a rope seal for placement at each interface between a bucket hook and a groove into which the bucket hook is inserted. In one embodiment, the seal is a braided rope seal formed of a braided metal sheathing that surrounds a ceramic composite matrix. This is stated to provide flexibility and high temperature resistance, and also retain some resiliency.
The above cited patents are incorporated by reference herein for their respective teachings. However, it is recognized that the above-cited, as well as various other prior art devices, are either expensive to manufacture, complicated to install, or lack sufficient sealing effectiveness for modern combustion turbine applications that operate at increasingly elevated temperatures.
Accordingly, there remains a need to provide an improved sealing element for sealing between the platforms of adjacent rotating blades in a turbo-machine, between adjacent vanes, and for other sealing functions in a turbo-machine. There also remains a need to provide a device for sealing that can be manufactured by appropriate modification of known manufacturing techniques, that is easy to install and to remove, and that provides improved sealing effectiveness.